Three new article modules: configuration binding, profiles and config data, Spring AOP

configuration-properties/  @ConfigurationProperties vs @Value on Spring Boot 4.1.1.
  The relaxed-binding matrix is generated by binding each spelling rather than
  transcribed, and re-checked against real processes -- the in-process probe was
  wrong twice before it was right. Records the three findings that came out of it:
  @Value does get relaxed resolution inside Spring Boot (Boot attaches
  ConfigurationPropertySources), the configuration processor silently stops
  generating metadata on JDK 23+ when declared as a plain dependency, and @Valid is
  not what makes nested constraints run.

profiles-and-config/       Precedence, profiles, spring.config.import and config trees.
  /precedence reports every source holding a property in rank order with file and
  line, which turns "my profile file had no effect" into a two-line answer. Also
  pins the counterintuitive one: an imported file outranks the file that imported it.

spring-aop/                Designators, proxy types, and aspects that do not fire.
  One advice per supported designator so the reference table is generated from real
  matches; all fourteen unsupported designators fed to the parser. Two corrections to
  the reference documentation: unsupported designators throw
  UnsupportedPointcutPrimitiveException (extends RuntimeException, not
  IllegalArgumentException), and spring-boot-starter-aop was renamed to
  spring-boot-starter-aspectj in Boot 4.

19 contract tests across the three modules, 15 captured transcripts, all regenerated
by scripts/run-all.sh. Verified on Spring Boot 4.1.1, Spring Framework 7.0.9,
JDK 25.0.4.1.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Gip4srpzMwjgoba6uEfbr5

profiles-and-config/docs/output/03-config-tree.txt

@@ -0,0 +1,45 @@
+== what Kubernetes actually mounts ==
+$ find /tmp/demo-configmap /tmp/demo-secret -type f | sort
+<configmap-mount>/demo.datasource-url
+<configmap-mount>/demo.greeting
+<configmap-mount>/demo.pool-size
+<configmap-mount>/demo/nested/value
+<secret-mount>/demo.api-key
+
+$ cat <configmap-mount>/demo.greeting; echo
+from-configmap-volume
+
+Each file holds a bare value with no trailing newline and no key. There is no
+properties syntax to parse -- the filename is the key.
+
+== importing it ==
+$ java -jar target/profiles-and-config-1.0.0.jar \
+    --spring.config.import=configtree:/tmp/demo-configmap/,configtree:/tmp/demo-secret/
+
+  active profiles : (none)
+  effective value : from-configmap-volume
+    1. from-configmap-volume              <- ConfigTreePropertySource {name='Config tree '/tmp/demo-configmap''}
+    2. from-application-yaml              <- 'file application.yaml' via location 'optional:classpath:/''}
+  holders that lost: 1
+
+  demo.pool-size      = 25
+  demo.nested.value   = from-nested-directory
+  demo.api-key        = sk_live_not_a_real_key
+
+A directory under the mount becomes a nested property: demo/nested/value is
+demo.nested.value. That is how a ConfigMap with slashes in its keys arrives.
+
+== the part that surprises people ==
+An imported config tree outranks application.yaml, but it is still config data,
+so it still loses to an environment variable:
+
+  active profiles : (none)
+  effective value : from-environment-variable
+    1. from-environment-variable          <- OriginAwareSystemEnvironmentPropertySource {name='systemEnvironment'}
+    2. from-configmap-volume              <- ConfigTreePropertySource {name='Config tree '/tmp/demo-configmap''}
+    3. from-application-yaml              <- 'file application.yaml' via location 'optional:classpath:/''}
+  holders that lost: 2
+
+There is also no such thing as a profile-specific config tree. There is no
+<mount>-prod directory convention; a per-environment ConfigMap is a different mount
+chosen by the deployment, not by spring.profiles.active.